The invention relates to vacuum-switch apparatus which includes at least one switching vessel and an actuator. The actuator is connected to the movable contact of the switching vessel by drive members and a contact pressure-spring is interposed between them.
Vacuum switchgear of this kind is described, for instance, in Deutsche Offenlegungsschrift 1,815,722. The purpose of the contact pressure-spring is to make available a further contact force in addition to the contact force between the contacts of the switching vessel caused by the ambient air pressure. This is important particularly if a larger contact force is required than can be obtained by the air pressure or if far-reaching independence of the contact force from the air pressure is to be accomplished.
In the operation of vacuum-switch apparatus, there is the problem that the state of the switching vessels and particularly, of the contacts, is not directly visible. But if reliable operation is to be assured at all times, the switching vessels must be replaced if the burn-off of the contacts has become excessive. Accordingly, it is an object of the invention to provide an indicating arrangement for a vacuum-switch apparatus of the kind described above which enables the burn-off of the contacts to be recognizable without difficulty.